lipl-4 Research Notes
Gene Overview
lipl-4 (K04A8.5) encodes a lysosomal acid lipase in C. elegans with sequence and functional similarity to human LIPA (lysosomal acid lipase). It is a key enzyme in the lysosome-to-nucleus retrograde lipid signaling pathway that promotes longevity.
Core Pathway: LIPL-4 → LBP-8 → NHR-49/NHR-80
The central discovery is that LIPL-4 generates lipid signaling molecules in the lysosome, which are then transported to the nucleus by the lipid chaperone LBP-8 to activate transcription factors NHR-49 and NHR-80 PMID:25554789.
Key lipid signals produced by LIPL-4:
- Oleoylethanolamide (OEA) - an N-acylethanolamine fatty acid derivative. OEA directly binds LBP-8 (with ~3x higher affinity than fatty acids) and NHR-80 (Kd ~7.8 µM). OEA supplementation extends lifespan PMID:25554789.
- Omega-6 PUFAs (AA, DGLA) - these activate autophagy, extending lifespan PMID:23392608.
Enzymatic Activity
- Triacylglycerol lipase (EC 3.1.1.3) PMID:21906946
- Lipid hydrolysis activity decreased in lipl-4(tm4417) loss-of-function at pH 4.5 but not pH 7.4 PMID:25554789
- Optimal at acidic pH (consistent with lysosomal function)
Subcellular Localization
Longevity Function
- Constitutive expression extends lifespan by ~55% PMID:25554789
- Requires lysosomal localization (no SP version has little lifespan effect) PMID:25554789
- Requires LBP-8, NHR-49, and NHR-80 for longevity effect PMID:25554789
- Required for germline-less (glp-1) longevity PMID:21906946
- Additive with dietary restriction (eat-2) longevity PMID:25554789
Autophagy Connection
- LIPL-4 overexpression induces autophagy PMID:21906946
- Autophagy required for LIPL-4-mediated longevity PMID:21906946
- LIPL-4 and autophagy are interdependent: autophagy maintains LIPL-4 lipase activity; lipl-4 required for autophagy induction PMID:21906946
- Omega-6 PUFAs produced by LIPL-4 activate autophagy in both worms and human cells PMID:23392608
Regulation
- Upregulated by fasting in intestine [PMID:23392608, PMID:23604316]
- Regulated by MXL-3 and HLH-30 (TFEB homolog) transcription factors PMID:23604316
- Induced in germline-less animals (glp-1) in a DAF-16-dependent manner PMID:21423649
- TOR inhibition induces lipl-4 expression PMID:21906946
Downstream Signaling
- LIPL-4 Tg increases acs-2 transcription >15-fold (NHR-49/NHR-80 dependent) PMID:25554789
- Promotes mitochondrial beta-oxidation PMID:30713071
- OEA production requires NAPE-PLD (nape-1) PMID:25554789